[moved] Supercharged VR running real badly :( need help

[Conky 0]

Hi chaps, about a week ago we bought a supercharged vr6 golf track car from a guy down south. We were told the car had been built from the ground up by a guy called Vince from Stealth racing , the engine was rebuilt to an awesome spec!

The problem is, pretty much from day one the car had a flat spot at around 4k, pretty nasty at times leading to the car not wanting to rev strongly until it reached 5k, its basically got worse and worse.

Yesterday we took the car up to my bros works garage and popped it on their Snap-on diagnostic tool, it was real helpful for once and told us there was a short to ground along the MAF circuit. Straight away we checked out the MAF sensor and noticed its 4 pin connector plug had been rubbing pretty badly against a strut brace mounting bolt and could see exposed wire, we started to unravel the wiring connecting to the MAF sensor only to find the insulation on the wire had melted real deep into the ecu loom all the way to the fuse/relay panel (plug G2), the top of the MAF connector had obviously shorted to the strut brace and really heated up the MAF power supply cable, fair bit of current to do that!!

Here was the damage:

First thing we did was rewire the melted cable (red/blue + supply to MAF) and check the ground cable (Brown –battery ) then once we did that we did a few checks on the MAF. We checked the earth connection, the supply voltage and checked the signal from the maf (we got 0.8-0.9v at idle and 1.6-1.7v at 3,000rpm) they all checked out as fine. Almost certain the problem had been sorted we took it out for a run but no change, still lumpy as hell!!

We went back, still concentrating on the MAF, we checked the twisted pair signal cable from the MAF to the ecu, it had no shorts or breaks but what we did notice the area around pin 16 of the ecu plastic socket had melted (pin 16 and 17 are the input for the MAF sensor)

We then checked out inside the ECU, obviously there would be nothing visible but it did have a pretty burnt electrical smell to it, which I’m sure shouldn’t have been there. the melted pin and smell may have nothing to do with the lumpy running but its all we can find.

That’s basically where we’re at, the diagnostic tool throws up no errors now but the car still runs like crap.

We're now at a loss and have nothing else to check over.

Any help would be most appreciated! is there a way to check the ecu to see if its reading the MAF signal at all???

Cheers

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Moderator edit by: cadguy

[rodney 17]

traditionally the car runs like a bag of spanners if the MAF sensor is dirty... Happens more freequently on charged cars... did you Clean the MAF? - link on here somewhere

also the lambda could add to that...Are you CAT free?........again they go on charged cars.. What plugs/leads/coil you running??

All those symptons can be attributed to items like this...

As I understand it there is no way other than to have the remap software hooked up to tell what is happening signal wise..... Vince @ Stealth is always worth a call if none of the normal things work..

I add these as it is always easy to get drawn into a complicated thing when all it is you forgot was high grade fuel..

Good luck. Hope it helps in some small way

[Conky 0]

Hi there mate, like I said we tested the voltage output of the MAF at idle and 3000rpm and its output was as expected, I cleaned it today just for peace of mind and it made little difference.

Its fitted with NGK-R's which look fine, new looking magnecor electrosport 80 leads and the OBD2 wasted spark setup and de-cat'ed

We still keep getting one fault code from our diagnostic tool

"00553 MASS AIR FLOW SENSOR-G70 SHORT WITH POWER"

We just cant see why we're still get this fualt code when the power and ground to the MAF checks out and the MAF output works fine all the way to the ECU plug giving what seems like a perfect signal.

Our diagnostic tool provides us with some live data, it gives an Air Flow reading in g/s which increases as you increase the rpm, we still get a reading even when the MAF is disconnected!! I cant understand how this is possible!? is this reading provided by some other sensor??

Cheers

[Conky 0]

Just had a chat with Vince and he says this fault code will never go away as long as it has a supercharger bolted to it. ecu will always read it as an incorrect value.

says my ecu should not smell like its been on a bbq and the melted plastic socket around pin 16 is real suspect. me thinks ecu is dead

[IbiVR 0]

Only cos his code doesnt adjust for increased airflow.... not entirly fair to blame the maf for the fault code...

Either way shouldnt melt the wire. That wire supplys 12v to alot of things, MAF, injectors etc. I'd look at changing the loom to really.

Tom.

[Conky 0]

didn’t blame the maf mate, like I said I've tested the MAF and it checked out.

Yes the supply (not specifically the wire that comes out of pin 8 in the g2 block) that feeds the MAF also supplies the EVAP valve, injectors heater element on the o2 sensor and also the fuel pump. all this has been checked and tested.

Cheers